Swap Landscape Parent material using Blueprint??

hi - Seeking advice on how to swap out a parent landscape material in a blueprint. I’m not asking about the landscape proxies, but the parent in a partitioned open world. I have been able to figure out how to swap out the partitioned proxies underneath the parent. But nothing actually shows up in game because the parent landscape actor still has the original material attached to it. So I’m wondering how we can interface with that exactly?